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1.
作者针对临床及亚临床乳房炎奶牛乳汁中金黄色葡萄球菌分离株的毒素基因进行检测和脉冲场凝胶电泳(PFGE)基因分型,比较2种类型乳房炎金黄色葡萄球菌分离株的差异.无菌法采集奶样,采用国际标准方法从中分离金黄色葡萄球菌,用多重PCR方法扩增nuc基因和mecA基因以确证金黄色葡萄球菌(SA)和耐甲氧西林金黄色葡萄球菌(MRSA).进一步用PCR方法检测SA的各种毒素基因(SEs、ETs、TSST 1和PVL基因等).利用限制性内切酶Sma Ⅰ对SA基因组DNA进行酶切和PFGE分析,最后利用BioNumerics软件进行聚类分析.结果:19.3％(23/119)的临床乳房炎奶样和14.8％(26/176)的亚临床乳房炎奶样确定为金黄色葡萄球菌阳性样品,分别从中分离鉴定出43株和26株金黄色葡萄球菌,其中临床乳房炎分离株中有5株为mecA基因阳性.临床乳房炎奶牛奶样中检测到SA的SEA、SEB、SED、SEJ和PVL毒素基因,检出率分别为3.8％(1株)、11.5％(3株)、19.2％(5株)、7.7％(2株)和31.2％(10株);亚临床乳房炎奶牛乳样中仅检测到SA的SEA和PVL毒力基因,检出率分别为7.0％(3株)和84.1％(37株).表明临床与亚临床乳房炎奶牛乳汁中SA菌株携带的毒素基因不一样,SEs可能是临床乳房炎菌株的重要致病基因,PVL可能是亚临床乳房炎菌株的重要致病基因.69株SA使用Sma Ⅰ酶切分型后,可分为7个大簇、50个基因型,来源相同的SA分型后大部分位于同一簇内.临床乳房炎奶牛乳汁中检测到MRSA菌株,PVL基因在亚临床乳房炎中的检出率为临床乳房炎的2.7倍.PFGE方法能较好的区分临床乳房炎和亚临床乳房炎的SA分离菌株. 相似文献
2.
奶牛乳房炎金黄色葡萄球菌的分离鉴定及毒力基因检测 总被引：1，自引：0，他引：1
《中国兽医学报》2019,(2):323-327
为研究奶牛乳房炎金黄色葡萄球菌毒力基因的分布情况,本试验通过MALDI Biotyper系统对分离自3个奶牛场的25株金黄色葡萄球菌进行鉴定及聚类分析,并采用PCR方法对25株金黄色葡萄球菌的nuc、clfA、fnbA、fn-bB、tsst-1、sea、seb和sec等14种毒力基因进行检测。结果显示,25株金黄色葡萄球菌被分为3个类群,各个类群之间及类群内菌株遗传距离较远。14种毒力基因中有7种被检出,检出率分别是nuc(100%)、fnbA (100%)、seg(64%)、clfA(52%)、fnbB(32%)、tsst-1(16%)和sea(4%),其余未检出。结果表明,不同奶牛场甚至同一奶牛场内存在多种金黄色葡萄球菌的流行株,且金黄色葡萄球菌携带毒力基因的数量和种类不同,并存在多种毒力基因组合,为奶牛金黄色葡萄球菌性乳房炎的防治提供基础研究。 相似文献
3.
隐性乳房炎患牛与健康牛外观无异,不易判断,对奶牛业造成的损失严重.金黄色葡萄球菌是引起隐性乳房炎的重要病原菌,准确判断金黄色葡萄球菌型隐性乳房炎是预防和控制乳房炎的重要途径.目前国际上普遍采用乳中体细胞数(SCC)作为检测隐性乳房炎的主要指标,但是约40％的金黄色葡萄球菌型乳房炎牛乳汁中SCC低于20万/mL.笔者依据相邻两月SCC差值高低,采集两个奶牛场荷斯坦牛生产群第一胎泌乳牛奶样65头份,从中检出有6头份含金黄色葡萄球菌.用PCR方法扩增金黄色葡萄球菌和耐甲氧西林金黄色葡萄球菌(MRSA)的特异基因nuc和mecA,结果发现,nuc基因检出率为100％(12/12),未检测到mecA基因.进一步用多重PCR方法检测金黄色葡萄球菌各种毒素基因,其中PVL基因在高SCC与低SCC奶样中的检出率分别为33.3％和100％,差异显著,这可能与PVL破坏白细胞有关.PFGE分型结果表明,所检测到的金黄色葡萄球菌可分为4个簇、5种类型,其中P2型(PVL)为流行株.结果提示,在荷斯坦牛生产群中,如果奶牛产奶量有所下降而SCC也不高时,应辅以分子检测手段来判断是否患有金黄色葡萄球菌型隐性乳房炎. 相似文献
4.
《动物医学进展》2021,42(6)
为研究甘肃地区牛源金黄色葡萄球菌(Staphylococcus aureus)的耐药情况、基因型总体结构特征及毒力因子的分布情况,从甘肃省东、中和西部3个地区的3个县市采集41头罹患临床型乳房炎奶牛的93份乳样,采用鉴别培养基分离纯化细菌。采用K-B法对分离株进行耐药性分析,常规PCR方法检测mecA抗性基因和14种常见毒力基因以及多位点序列分型(multilocus sequence typing, MLST)。结果显示,93份乳样中分离出28株金黄色葡萄球菌;分离株有不同程度的耐药且多为多重耐药(16株),多重耐药菌株占57.14%,未发现耐万古霉素菌株(VRSA),万古霉素敏感率为100%;28株分离菌中共检出mecA阳性11株,检出率为39.3%;共获得9个已知ST型;有12种毒力基因不同程度被检出,其中nuc、spa和coa检出率为100%,hlb、set1、clfA、FnBPA和seb阳性检出率均大于50%,sak、seg、PVL和sea的检出率依次为28.6%、7.9%、14.3%和21.4%,而FnBPB、hla基因未检出。研究结果可为甘肃省牛源金黄色葡萄球菌的耐药性评价、溯源分析和治疗提供参考依据。 相似文献
5.
奶牛乳房炎致病型耐甲氧西林金黄色葡萄球菌的分离鉴定 总被引：1，自引：0，他引：1
为探究引起奶牛乳房炎的耐药性致病菌,本研究针对西安地区显性乳房炎奶样中的耐甲氧西林金黄色葡萄球菌（MRSA）进行系统研究。采用常规细菌学鉴定法对34头（次）荷斯坦牛76个乳区152份奶样的金黄色葡萄球菌（Staphylococcus aureus,S.aureus）进行了分离培养,共检出92株阳性菌株,检出率为60.5%;对其进行S.aureus致病基因nuc的特异性PCR检测,共检出28株含nuc基因的阳性菌株,检出率为30.4%;进一步针对MRSA耐药基因mecA进行特异性PCR扩增,共检出5株MRSA,检出率为17.9%。研究结果为MRSA耐药菌的有效检测及奶牛乳房炎的治疗提供了指导。 相似文献
6.
奶牛乳房炎金黄色葡萄球菌黏附素研究进展 总被引：1，自引：0，他引：1
金黄色葡萄球菌的黏附素是其引起奶牛乳房炎的关键因素之一,与金黄色葡萄球菌在奶牛乳房中定植有关的的黏附素主要是ClfA、FnBPA和FnBPB3种。曾有对金黄色葡萄球菌黏附素表达调控的研究发现,在金黄色葡萄球菌感染的早期主要表达黏附素,之后才表达毒素和荚膜,所以人们认为,对金黄色葡萄球菌的黏附进行干预,可以减少或阻止毒素和荚膜的表达,而以黏附素作为靶位进行疫苗研制可能是预防奶牛金黄色葡萄球菌性乳房炎的有效途径。国外对金黄色葡萄球菌的黏附素的研究历史相对较久,并且也取得了许多可喜成绩,而国内对金黄色葡萄球菌的研究相对滞后。因此,研究金黄色葡萄球菌黏附素对预防由金黄色葡萄球菌引起的奶牛乳房炎具有广阔的前景。 相似文献
7.
《黑龙江畜牧兽医》2020,(12)
为了了解重庆市荣昌区、永川区和巴南区奶牛乳房炎葡萄球菌的种类和生物膜相关基因的流行现状,试验对从重庆市荣昌区、永川区和巴南区18个奶牛养殖场分离得到的127株葡萄球菌采用全自动生化鉴定和葡萄球菌特异性基因dnaJ扩增及测序分析法进行葡萄球菌种的鉴定,并采用多重PCR扩增法进行毒力基因检测。结果表明:从127株葡萄球菌中鉴定出20种葡萄球菌,其中表皮葡萄球菌占18.90%,溶血葡萄球菌占12.60%,阿尔莱特葡萄球菌占11.81%,金黄色葡萄球菌占3.15%;采用多重PCR方法检测127株葡萄球菌的eno、clfB和fib等14个毒力基因,其中eno基因检出率高达40.16%,clfB基因检出率高达18.11%,未检测到icaB和icaC基因。说明引起本地区奶牛乳房炎流行的葡萄球菌以凝固酶阴性葡萄球菌为主,而非金黄色葡萄球菌,应加强对表皮葡萄球菌等凝固酶阴性葡萄球菌的临床防控。 相似文献
8.
奶牛源金黄色葡萄球菌新疆流行株的耐药特性、毒力基因及分子分型 总被引：2，自引：0，他引：2
旨在了解引起奶牛乳房炎和子宫内膜炎的金黄色葡萄球菌(SA)新疆流行株的耐药性、毒力基因及其分子流行病学特征。对2014—2016年新疆地区155株SA奶牛临床分离株的耐药表型进行分析,并对耐甲氧西林SA(MRSA)进行鉴定;通过PCR技术对SA的耐药基因、毒力基因进行检测及SCCmec、MLST分子分型。结果在155株SA中检出22株MRSA,检出率为14.2%;MRSA流行株的耐药性明显高于甲氧西林敏感SA(MSSA);不同的毒力基因在MSSA和MRSA中的检出率有所差异;SCCmecⅠ为新疆地区SA主要基因型;MLST分型共检出14种ST型,分别为ST188、ST584、ST9、ST805、ST2373、ST968、ST2139、ST1、ST2700、ST903、ST2454、ST2990、ST63、STX,其中ST1和ST9检出率相对较高,在MSSA菌株中ST9型的检出率最高,MRSA菌株中ST1检出率最高。研究表明,新疆地区奶牛源SA中主要流行株为MSSA,但MRSA耐药性更强,且毒力基因分布多样,ST9为MSSA流行株的主要基因型,ST1-SCCmecⅠ为MRSA流行株的主要基因型。 相似文献
9.
本试验对由患慢性奶牛乳房炎奶样中分离出的1株疑似金黄色葡萄球菌小菌落突变株(SCVs)进行形态观察、金黄色葡萄球菌相关保守基因片段(nuc、nucA、16S rDNA) 多重PCR扩增鉴定、药敏试验、生理生化特性研究及补偿试验。结果显示分离出1株金黄色葡萄球菌SCVs,该菌含有金黄色葡萄球菌菌种特异性基因nuc和nucA;与金黄色葡萄球菌质控菌株ATCC 25923的抑菌圈大小明显不同;菌落形态主要表现为菌落细小、生长缓慢、溶血能力下降;凝固酶活性下降;耐盐能力降低;革兰氏染色为革兰氏阳性球菌,呈葡萄状排列;补偿试验鉴定该金黄色葡萄球菌SCVs为胸腺嘧啶依赖型。结果表明成功分离鉴定出1株胸腺嘧啶依赖型金黄色葡萄球菌SCVs,为由金黄色葡萄球菌SCVs引起的奶牛慢性乳房炎的预防和控制及其致病机制的研究奠定前期基础。 相似文献
10.
为了调查内蒙古某牛场隐性乳房炎奶牛牛乳中金黄色葡萄球菌和大肠杆菌的分布情况及其对常用临床抗菌药物的耐药性,试验采集该牛场102份乳样,应用兰州乳房炎检测法检测奶牛隐性乳房炎,并对乳样中2种病原菌进行分离鉴定、药敏试验。结果表明:采集的102份乳样中有35份呈隐性乳房炎阳性,其中重度隐性乳房炎8份,中度隐性乳房炎11份,轻度隐性乳房炎16份,奶牛隐性乳房炎的检出率为34.31%(35/102)。从102份乳样中共分离得到20株大肠杆菌和15株金黄色葡萄球菌,20株大肠杆菌对庆大霉素、美罗培南、环丙沙星、磷霉素敏感,对四环素、头孢他啶、氟苯尼考的耐药率分别为5%(1/20)、5%(1/20)、50%(10/20);15株金黄色葡萄球菌对四环素、万古霉素、氟苯尼考敏感,对泰妙菌素、青霉素、苯唑西林、红霉素、卡那霉素的耐药率分别为33.3%(5/15)、53.3%(8/15)、46.7%(7/15)、6.7%(1/15)、13.3%(2/15)。说明庆大霉素、美罗培南、环丙沙星、磷霉素、万古霉素可以作为该奶牛场的候选药物。 相似文献
11.
Eric Vautor Joshua Cockfield Caroline Le Marechal Yves Le Loir Marl��ne Chevalier D. Ashley Robinson Richard Thiery Jodi Lindsay 《Veterinary research》2009,40(6)
Staphylococcus aureus mastitis in dairy sheep ranges from subclinical mastitis to lethal gangrenous mastitis. Neither the S. aureus virulence factors nor the host-factors or the epidemiological events contributing to the different outcomes are known. In a field study in a dairy sheep farm over 21 months, 16 natural isolates of S. aureus were collected from six subclinical mastitis cases, one lethal gangrenous mastitis case, nasal carriage from eight ewes and one isolate from ambient air in the milking room. A genomic comparison of two strains, one responsible for subclinical mastitis and one for lethal gangrenous mastitis, was performed using multi-strain DNA microarrays. Multiple typing techniques (pulsed-field-gel-electrophoresis, multiple-locus variable-number, single-nucleotide polymorphisms, randomly amplified polymorphic DNA, spa typing and sas typing) were used to characterise the remaining isolates and to follow the persistence of the gangrenous isolate in ewes’ nares. Our results showed that the two strains were genetically closely related and they shared 3 615 identical predicted open reading frames. However, the gangrenous mastitis isolate carried variant versions of several genes (sdrD, clfA-B, sasA, sasB, sasD, sasI and splE) and was missing fibrinogen binding protein B (fnbB) and a prophage. The typing results showed that this gangrenous strain emerged after the initial subclinical mastitis screening, but then persisted in the flock in the nares of four ewes. Although we cannot dismiss the role of host susceptibility in the clinical events in this flock, our data support the hypothesis that S. aureus populations had evolved in the sheep flock and that S. aureus genetic variations could have contributed to enhanced virulence. 相似文献
12.
Vautor E Magnone V Rios G Le Brigand K Bergonier D Lina G Meugnier H Barbry P Thiéry R Pépin M 《Veterinary microbiology》2009,133(1-2):105-114
Staphylococcus aureus is recognized worldwide as a major pathogen causing clinical or subclinical intramammary infections in lactating sheep, goats and cows. The present study was carried out to compare 65 S. aureus isolates mainly obtained from nasal carriage and subclinical mastitis in dairy sheep and 43 isolates obtained from subclinical mastitis from 22 goats and 21 cows. A DNA microarray, containing probes against 190 true or putative virulence factors, was used to detect the presence of the virulence genes. Their presence/absence was independently assessed by PCR for the genes of interest. Sheep isolates obtained from the nostrils or the udders did not show any significant tissue specific virulence factor. The dominant pulse-field electrophoresis profile (OV/OV'), associated with spa clonal complex spa-CC 1773, matched mainly with the agr group III and was only found in ovine and caprine isolates. This clone was more specifically characterized by the prevalence of the following virulence genes: lpl4, ssl6, bsaA1, bsaB, bsaP, SAV0812. Moreover, seven virulence-associated genes (lpl1, sel, sec, tst, lukF-PV-like component, lukM, SAV0876) were associated with isolates from small ruminants, while the egc cluster, fhuD1, abiF and SAV2496 with bovine isolates. This genomic study suggests the existence of lineage- and host-specific genes leading to the development of host-specific pathogenic traits of S. aureus isolates. 相似文献
13.
Staphylococcus aureus is a major pathogen for cattle, causing various forms of subclinical and clinical mastitis. Two groups of virulence factors (leukotoxins and superantigens) are supposed to play an important role in the initiation and/or the exacerbation of this disease. In order to detect all known and putative members of leukotoxins and SAgs (superantigens), we tested secreted factors of different S. aureus isolates in flow cytometry-based assays.Isolates were sampled from 68 cows of different farms and cultured for 24h in vitro. Supernatants were then coincubated with purified polymorphonuclear granulocytes (PMN) or combinations of blood mononuclear cells (MNC) and PMN. Viable PMN and MNC were determined by quantitative flow cytometry. In addition, we recorded the proliferation-inducing potential of isolate supernatants for bovine MNC. Based on these criteria, the supernatants of S. aureus isolates fell in three groups. The first group (n=32), termed LT-SNs (leukotoxin-containing supernatants), killed purified granulocytes (neutrophils and eosinophils) in vitro. The second group of supernatants (n=20), termed SAg-SN (superantigen-containing supernatants), induced activation and proliferation of mononuclear cells (MNC) and, only in the presence of MNC, resulted in a selective depletion of neutrophils after 24h in vitro. The third group of supernatants (n=16) contained neither LTs or SAgs. Functionally, SAg-SNs behaved like purified staphylococcal enterotoxin A (SEA) or SEB tested in parallel. The absence of SAg-like activity in LT-SNs was confirmed by heat treatment of LT-SNs, which destroyed the leukocytotoxic activity, but did not reveal any MNC-activating potential. This study, therefore, suggests, that pathogenic S. aureus isolates either produce leukotoxins or superantigens and that both groups of virulence factors can easily be differentiated by the functional assays described.The prevalence of leukotoxin- or superantigen-producing isolates was comparable among cattle with subclinical (LT=41%; SAg=30.8%) mastitis. The higher frequency of LT-producing isolates in cases of clinical mastitis (LT=55.2%; SAg=27.6%) was not significant. At least, these findings argue against the dominant role of superantigens or leukotoxins in S. aureus-induced bovine mastitis. 相似文献
14.
F. N. Costa N. O. Belo E. A. Costa G. I. Andrade L. S. Pereira I. A. Carvalho R. L. Santos 《Tropical animal health and production》2018,50(5):1089-1097
Staphylococcus aureus is among the microorganisms more frequently associated with subclinical bovine mastitis. S. aureus may produce several virulence factors. This study aimed at determining the frequency of virulence factors such as enterotoxins, toxic shock syndrome toxin 1, and ica adhesion genes. In addition, we assessed antimicrobial drug resistance in S. aureus isolated from clinical and subclinical cases of mastitis. A total of 88 cows with clinical or subclinical mastitis were sampled, resulting in 38 S. aureus isolates, from which 25 (65.78%) carried toxin genes, including seb, sec, sed, tst, and icaD adhesion gene. These S. aureus isolates belong to 21 ribotypes and three S. aureus strains belonged to the same ribotype producing ica adhesion gene. Approximately 90% of S. aureus strains obtained in our study demonstrated multiple resistance to different antimicrobial agents. The most efficacious antimicrobial agents against the isolates were gentamicin, amoxicillin, and norfloxacin. Gentamicin was the most efficacious agent inhibiting 78.95% of the S. aureus isolates. The least efficacious were penicillin, streptomycin, and ampicillin. Our results can help in understanding the relationship between virulence factors and subclinical mastitis caused by S. aureus. Further research about diversity of S. aureus isolates and genes responsible for the pathogenicity of subclinical mastitis is essential. 相似文献
15.
Staphylococcus aureus is recognized worldwide as a pathogen causing many serious diseases in humans and animals, and is the most common aetiological agent of clinical and subclinical bovine mastitis. The importance of evaluating the combination of S. aureus virulence factors has been emphasized both in human and veterinary medicine, and knowledge about the genetic variability within different S. aureus populations would help in the design of efficient treatments. The aim of the present study was to determine the genetic profiles of S. aureus strains isolated from milk of cows suffering from clinical and subclinical mastitis in Belgium. The presence of about forty virulence-associated genes was investigated by specific polymerase chain reaction (PCR) amplification. A high number of genotypic subtypes were observed, demonstrating further the large variation in the presence of virulence genes in S. aureus isolates and the considerable diversity of strains populations that are able to cause mastitis in cows. In accordance with other studies, we showed that some genes are associated with mastitis-causing S. aureus isolates, whereas others are absent or rarely present. We also further highlighted the presence of conserved gene combinations, namely the enterotoxigenic egc-cluster and the bovine pathogenicity island SaPIbov. Importantly, the presence of isolates carrying genes coding for toxins involved in important human infections makes the milk of cows with mastitis a potential reservoir for these toxins, and therefore a potential danger in human health, which strengthens the importance to consider raw milk consumption and its processing very carefully. 相似文献
16.
为分离临床型奶牛乳房炎中的肠球菌,检测其耐药性和携带毒力基因的情况,本试验采集了甘肃省东、中和西部3个地区41头临床型乳房炎奶牛的奶样93份,并构建了肠球菌毒力基因的原核表达载体。试验使用选择性培养基分离纯化肠球菌,16S rRNA和生化试验结合的方法鉴定所分离菌株的种;选取16种抗菌药进行药敏试验;常规PCR方法检测11种毒力基因的携带情况,最后对具有免疫原性的毒力基因进行原核表达载体的构建。鉴定结果显示,93份乳样中18株为肠球菌,并分为9种。药敏结果显示,分离株多数为多重耐药菌（multiple resistant bacteria,MDR）,占88.89%,未发现耐万古霉素菌株（vancomycin-resistant enterococcus,VRE）,万古霉素敏感率94.12%,所有分离株至少对一种抗菌药耐药。PCR检测结果表明,11种毒力基因均有检出,cob基因检出率最高（44.44%）,efaA、hyl、ccf和esp基因检出率分别为33.33%、27.78%、27.78%和22.22%,Asa1、cylA、EF3314和gelE基因检出率均为16.67%,Ace和cylM基因检出最低（11.11%）;毒力基因组合因菌种不同而存在差异,选择具有免疫原性的Ace和gelE基因成功构建出原核表达载体pET32a-Ace和pET32a-gelE。本试验为后续绘制3个地区奶牛乳房炎流行病学区域谱以及制备相应抗体和亚单位疫苗提供了基础数据及生物材料。 相似文献
17.
This study was carried out to determine the prevalence of coagulase-negative staphylococci in clinical and subclinical mastitis in commercial and small-scale farms in Zimbabwe. Thirty five quarter milk samples from clinical mastitis cases and 371 quarter milk samples from cows with subclinical mastitis were cultured for bacterial pathogens. The most frequent pathogens isolated in clinical mastitis were the enteric bacteria (31.4%), followed by coagulase negative staphylococci (22.9%) and then Staphylococcus aureus (17.1%), whereas in subclinical mastitis S. aureus (34.2%) and coagulase-negative staphylococci were (33.2%) the most common. Bacillus species were only isolated in milk samples from subclinical mastitis. Coagulase-negative staphylococci were observed in mixed infections with other bacteria in only 2.2 of the 406 milk samples from clinical and subclinical mastitis where they were isolated together with Bacillus species in 6 of the 9 mixed infection cases. About 95% of the milk samples from which 131 coagulase-negative staphylococci were isolated had correspondingly high somatic cell counts. The coagulase-negative staphylococci isolated most frequently were S. chromogenes (7.9%), S. epidermidis (7.4%) and S. hominis (5.9%). They were all associated with high somatic cell counts. All the coagulase-negative staphylococci isolates were susceptible to cloxacillin and erythromycin, and more than 90% of the isolates were susceptible to neomycin, penicillin and streptomycin. The highest resistance was to tetracycline (17.6%), followed by lincomycin (13.7%). About 8% of the isolates were resistant to both penicillin and streptomycin. 相似文献
18.
SHEN Yulong MEN Qianyun CHEN Tingting LI Zongshuai LI Haijiang YANG Yang ZHANG Yong ZHAO Xingxu 《中国畜牧兽医》2007,47(10):3389-3400
The aim of this study was to isolate Enterococcus in clinical dairy cow mastitis,detect its drug resistance and virulence genes,a total of 93 milk samples were collected from 41 dairy cosw with clinical mastitis in eastern,central and western regions of Gansu province,and then construct a prokaryotic expression vector for virulence genes.This experiment used selective medium to isolate and purify bacteria.16S rRNA and biochemical experiments combined method to identify the isolated strains.16 antibiotics were selected for drug sensitivity test,and conventional PCR method was used to detect the carrying of 11 virulence genes.Finally,the detected virulence genes with immunogenicity were selected for the construction of prokaryotic expression vectors.The separation and identification results showed that 18 strains of Enterococcus were isolated and identified from the 93 milk samples,which were divided into 9 species.Drug susceptibility results showed that most of the isolates were multiple resistant to bacteria,accounting for 88.89%.No vancomycin-resistant Enterococcus was found,vancomycin sensitivity rate was 94.12%,and all isolates were resistant to at least one antibiotic.Virulence gene test results demonstrated that 11 virulence genes were detected,the detection rate of cob gene (44.44%) was the highest,the detection rates of efaA,hyl,ccf and esp genes were 33.33%,27.78%,27.78% and 22.22% respectively,the detection rates of Asa1,cylA,EF3314 and gelE genes were all 16.67%,while Ace and cylM genes had the lowest detection rate (11.11%).The virulence genes combination was different due to different strains.Ace and gelE genes with immunogenicity were selected and the prokaryotic expression vector pET32a-Ace and pET32a-gelE were successfully constructed.The results provided basic data and biological materials for subsequent mapping of regional epidemiology of cow mastitis in three regions and preparation of corresponding antibodies and subunit vaccines. 相似文献
19.
Bean A Williamson J Cursons RT 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2004,51(6):285-287
Escherichia coli, a Gram-negative environmental pathogen associated with bovine mastitis was isolated from the milk of 34 symptomatic cows that had been diagnosed with clinical mastitis. Eighty isolates were obtained over a 17-month period and these isolates were screened by DNA amplification for the following E. coli virulence genes: cnf1, cnf2, eaeA, eagg, einv, ltx1, stx1, stx2 and vt2e. Thirty of the bacterial isolates, obtained from 23 different cows, had toxin genes identified in their DNA. The most common virulence gene detected was stx1, with a prevalence of 31%, followed by cnf2 (7.5%), vt2e (6.25%) and eaeA (4%). The possession of different virulence genes by the bacterial isolates had no discernable impact on the health status of the cows as there was no correlation between the potential for toxin production by the E. coli isolates and the systemic clinical condition of the respective infected cows. 相似文献